A lifting apparatus of this type is known from DE-0S 29 09 171. It functions in such a way that during normal operation, the easily movable arrester nut, a recirculating-ball nut for example, is driven upwardly and downwardly by the lifting carriage during the lifting and lowering movement, which is joined in a fixed manner with the vertically movable lifting platform, in conjunction with which the screw threading and the arrester nut are designed in such a way that no self-locking occurs.
If, for example, the chain that carries the lifting platform breaks, then instantly, as a result of the accelerated initial dropping movement of the lifting carriage, the latter comes to lie against the easily movable arrester nut, as a result of which at the same time the rotating movement of the arrester nut is prevented, and the lifting carriage is thus held securely on the arrester rod which is provided with screw threading. However, this known apparatus has the disadvantage that the braking action is not brought about until the lifting platform, and thus the lifting carriage, falls, and in conjunction with this, the stiffness of the compression spring that is placed between the lifting carriage and the arrester nut is very essential. Since the stiffness of the spring varies specifically within certain limits, the initiation of the braking effect is somewhat different as well.